1. Field of the Invention
The present invention relates to a plasma display apparatus, and more particularly, to the structure of a bus electrode and a transparent electrode, in which panel capacitance can be reduced.
2. Discussion of Related Art
In general, a plasma display panel is a display apparatus that implements predetermined images using a visible ray of red (R), green (G) and blue (B), which is generated by exciting phosphors with vacuum ultraviolet rays (VUV) radiated from plasma obtained through a gas discharge.
In the plasma display apparatus, a discharge cell is selected by a counter discharge between a scan electrode and an address electrode, and images are implemented by a surface discharge between the scan electrode and a sustain electrode.
More particularly, the construction of the plasma display apparatus will be first described. An upper substrate and a lower substrate opposite to the upper substrate are formed in the panel with them being combined together. A scan electrode, a sustain electrode and a dielectric layer are formed in the upper substrate.
In the lower substrate are formed a plurality of address electrodes, a dielectric layer for protecting the address electrodes and providing insulation, barrier ribs that partition the discharge cells, and a phosphor layer coated on the dielectric layer and the barrier ribs, for radiating a visible ray with a plasma discharge.
Furthermore, in the upper substrate is also formed a dielectric layer for protecting the scan electrode, the sustain electrode and the electrodes, and providing insulation. Each of the scan electrode and the sustain electrode consists of a bus electrode and a transparent electrode.
As a voltage is applied to any one of the address electrode, the scan electrode and the sustain electrode, an address discharge is generated and a discharge cell is selected. Furthermore, a sustain discharge is generated between the scan electrode and the sustain electrode, and images are displayed accordingly.
The structure of the bus electrode of the plasma display apparatus constructed above will be described with reference to FIG. 1 along with problems of the related art.
Referring to FIG. 1, a discharge space is partitioned by a barrier rib 23. Bus electrodes 11b are formed on the barrier rib with them being spaced apart by a margin (m1) of less than 20 μm from the discharge space. Furthermore, a width (d1) of the bus electrodes 11b in the related art is set to 55 μm to 80 μm.
In a process in which the upper substrate and the lower substrate are combined to form the panel, however, in the case where an alignment value of the upper substrate or the lower substrate exceeds tolerance error, the margin (m1) of the prior art bus electrode 11b was not sufficiently secured. Therefore, as shown at the right side of FIG. 1, the bus electrode infiltrates into the discharge space. Therefore, problems arise because a light-emission area from which a visible ray is radiated is decreased and luminance is lowered.
Furthermore, the shape of a transparent electrode 11a that is electrically connected to the prior art bus electrode 11b will be described below with reference to FIG. 2.
Referring to FIG. 2, the discharge space is partitioned by the barrier rib 23. The bus electrode 11b is formed on the barrier rib 23. The transparent electrode 11a that projects from the bus electrode 11b to the inside of the discharge space is also formed. It is to be understood that the transparent electrode 11a and the bus electrode 11b are scan electrodes Y connected to a scan driver in FIG. 2.
More particularly, a width (T1) of the transparent electrode 11a is set to be wider than a width (T2) of the bus electrode 11b so that a cross section of an overlapped area of the transparent electrode 11a and the bus electrode 11b becomes wide, as shown in FIG. 3. For example, the width (T1) of the transparent electrode 11a can be set to about 100 μm and the width (T2) of the bus electrode 11b can be set to about 80 μm.
That is, if a cross section where the metal bus electrode 11b and the transparent electrode 11a to which a driving signal is applied from the scan driver are overlapped with each other becomes wide, a sustain discharge is more smoothly generated. Therefore, in the related art, as shown in FIGS. 2 and 3, the width of the transparent electrode 11a projecting into the discharge space is formed to be wide.
As the width of the transparent electrode 11a is formed to be wider than that of the bus electrode 11b, however, an area where the transparent electrode 11a is overlapped with the barrier rib 23, which is indicated by a dotted line of FIG. 2, is also widened. Therefore, a problem arises because panel capacitance rises.
The term “panel capacitance” refers to that capacitance formed in a panel having a characteristic of storing energy by an electric field and inducing a current by voltage shift is equivalently represented.
However, there are problems such as that power consumption is increased and a waveform is distorted, etc. as panel capacitance is higher. For this reason, to reduce panel capacitance, a width of the electrodes formed in the upper substrate or the lower substrate, a gap between the electrode and the like need to be controlled.